In an earlier interview with Fairfax Media, the GP insisted he had done nothing illegal.

"This is a matter of principle. You have got a public health policy which is causing harm ..."

Dr Piesse and his colleague, naturopath Nerida James, attended a screening of the controversial anti-vaccination film Vaxxed in Hawthorn, where he told participants there were ways in which parents could get vaccination exemptions and that he knew of other doctors who were providing them.

"There are a few who are doing it as well, but they will get attacked as well," he said.

"The system cannot tolerate doctors who don't follow the government's line."

It is believed complaints will be lodged with the regulator over two other doctors in suburban practices who are also involved in promoting anti-vaccination messages.

Under "no jab, no play" legislation introduced in 2016, childcare services and kindergartens must first obtain evidence that a child is fully immunised for their age, on a catch-up vaccination program, or is unable to be fully immunised for medical reasons, before enrolling them.

Many parents involved in the anti-vaccination movement fear a link between the measles, mumps and rubella vaccine and autism. Such a link was first suggested in 1998 by UK researcher Andrew Wakefield.